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Tree-lined streets, like the ones seen here from Seoul, Korea, can have a significant impact in improving air quality in cities. Photo by Abby Yao.

A new study out of the University of Kent in the UK found that a 10 percent increase in urban tree coverage in mid-size cities, like Leicester, can absorb about 12 percent of carbon emissions, contributing to cleaner air. The study is yet another addition to the argument that any sound urban planning or transit policy to improve air quality must be supplemented with green spaces.

To reach their intuitive, yet essential, conclusion the conservation scientists first calculated tree density and vegetation on a city-wide scale, and later derived the biomass and carbon storage potential in each vegetation category. Based on their calculations, the researchers found that above-ground vegetation stores 231,521 tons of carbon, of which 97.3 percent is stored by trees.

And although the study brings some much needed positive news to the greenhouse gas debate, the researchers express the importance of maintaining this valuable resource for the city’s air quality.

“Although the quantities of carbon stored within the above-ground vegetation of Leicester are not trivial, it is not a permanent sink. The carbon captured as a plant grows will ultimately be released back into the environment when it dies or is destroyed, and replacement is therefore necessary to counterbalance the carbon emitted from removed vegetation. In some instances, trees lost in urban areas will be replaced through natural regeneration, but the majority are likely to require replanting to maintain current carbon reservoirs.This is of particular importance on publicly owned/managed land, where trees are frequently removed or subject to surgery in response to subsidence or human safety concerns.”

The study comes at a time when UK officials set a greenhouse gas reduction rate of 80 percent by 2050, based on the 1990 levels. With both the study and the realities of managing GHG emissions, the researchers highlight the importance of local authorities in accomplishing ambitious national goals.

“Local authorities are therefore central to national efforts to cut carbon emissions, although reductions required at city-wide scales are yet to be set. This has led to a need for reliable data to help establish and underpin realistic carbon emission targets and reduction trajectories, along with acceptable and robust policies for meeting these goals. Here, we have illustrated the potential benefits of accounting for, mapping and appropriately managing above-ground vegetation carbon stores, even within a typical densely urbanized European city.”